Normally, packets of cigarettes are fed from a cellophaning machine to a cartoning machine on a single pocket feed conveyor, which feeds the packets directly from the cellophaning machine to the cartoning machine in a single orderly succession, and so constitutes both an output conveyor of the cellophaning machine and an input conveyor of the cartoning machine. This solution has the obvious advantage of maintaining timing between the two machines, but also the obvious disadvantage of in no way allowing for compensating any gaps, i.e. empty pockets, on the transfer conveyor, and so preventing the formation of incomplete groups on the cartoning machine.
To compensate any gaps, it has been proposed to keep the output conveyor of the cellophaning machine separate from the input conveyor of the cartoning machine, and to interpose an interoperational (preferably FIFO) store between the two. The store is supplied by the output conveyor of the cellophaning machine with a first orderly succession of packets of cigarettes in time with the cellophaning machine; and the packets of cigarettes are brought together inside the store into queues, are withdrawn from the queues in the store by the input conveyor of the cartoning machine, and are again arranged into a second succession in time with the cartoning machine. As such, any gaps along the output conveyor of the cellophaning machine are compensated, but at the expense of a loss of synchronization of the two machines. What is more, at relatively high production speeds, withdrawing the packets of cigarettes from the queues in the store is not easy, and may result in damage to the packets of cigarettes.
Patent Application EP1721844A1 proposes a unit for feeding packets of cigarettes from a cellophaning machine to cartoning machine, in which a first pocket output conveyor of the cellophaning machine and a second pocket input conveyor of the cartoning machine travel continuously in first and second opposite directions respectively, and are connected to each other by a pocket transfer wheel interposed between the first and second conveyor. The pocket transfer wheel can be operated to rotate about an axis of rotation crosswise to the first and second conveyor; or to translate together with the second conveyor and crosswise to the axis of rotation to compensate one or more gaps on the first conveyor; or to translate together with the first conveyor and crosswise to the axis of rotation to form a succession of gaps, in time with the cartoning machine, on the second conveyor.
The feed unit in Patent Application EP1721844A1 has several drawbacks, by not allowing for positioning the heat-shrink devices as required to obtain high-quality plastic overwrappings of the packets of cigarettes, and by coping poorly with sharp deceleration (or sudden stoppages) of the cartoning machine. That is, given its greater inertia, the cellophaning machine cannot slow down or stop as fast as the cartoning machine, with the result that, in the event of sharp deceleration (or sudden stoppage) of the cartoning machine, a certain number of packets of cigarettes are inevitably fed onto the output conveyor of the cellophaning machine, and, not being feedable to the cartoning machine, are necessarily rejected.
Patent Application DE2618905A1 describes a transfer unit for transferring individual cigarettes between two conveyors, and for compensating any difference in the speed of the two conveyors. A first pocket output conveyor and a second pocket input conveyor travel continuously in first and second opposite, parallel directions respectively, and are connected to each other by a pocket transfer drum, which is interposed between the first and second conveyor, and rotates about an axis of rotation crosswise to the first and second conveyor to transfer cigarettes between the two conveyors. In the event of a difference in the speed of the two conveyors, the transfer drum translates, together with one of the two conveyors, in the first or second direction.
Patent Application DE1124584A1 describes a transfer unit for transferring products between two belt conveyors travelling at two different speeds, and for compensating the difference in the speed of the two conveyors. A first belt conveyor and a second belt conveyor travel continuously in first and second opposite, parallel directions respectively, and are connected to each other by a third belt conveyor, which is interposed between the first and second conveyor, and translates back and forth in the first or second direction.